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•  » Science: A bacteria doubles its population every 12 hours.

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cat1kf2
2012-11-22 15:38:55

#### mathgogocart wrote:

according to bob bundy(thank you)
the Awser is 25

cat1kf2
2012-11-22 15:30:00

#### bob bundy wrote:

hi cat1kf2

Welcome to the forum.

Work backwards:

After 3 days ....................1600

12 hours earlier................   1600 ÷ 2

after two days ..................  ÷ 2 again

12 hours earlier ................  ÷ 2 again

After one day ...................  ÷  2 again

12 hours ealier .................   ÷ 2 again

start ................................  ÷ 2 again

Bob

SMBoy
2012-11-19 22:00:55

Thank's all I understand now how it works.

mathgogocart
2012-11-19 12:46:26

according to bob bundy(thank you)
the Awser is 25

Ms_Zee
2012-11-19 11:37:52

Hi SMboy,
The explanation you received from bob bundy is correct, you just need to work out the result.

Hi;

The use of this site for personal advertising is forbidden. Everyone here is a volunteer. We have teachers, mathematicians, physicists, engineers, students and me all answering questions for nothing. If you would like to add your expertise to our group then that would be fine.

bob bundy
2012-11-18 19:59:11

hi SMboy,

Welcome to the forum.

I gave a method, but deliberately did not say what I thought the answer is.

Bob

SMBoy
2012-11-18 19:54:49

bob bundy
2012-11-16 19:07:22

hi cat1kf2

Welcome to the forum.

Work backwards:

After 3 days ....................1600

12 hours earlier................   1600 ÷ 2

after two days ..................  ÷ 2 again

12 hours earlier ................  ÷ 2 again

After one day ...................  ÷  2 again

12 hours ealier .................   ÷ 2 again

start ................................  ÷ 2 again

Bob

cat1kf2
2012-11-16 18:53:41

After 3 days, there are 1,600 bacteria. How many bacteria were there at the beginning of the first day? Use the work backward strategy.